Vent arrangement for respiratory mask

ABSTRACT

A control system provides automated control of gas washout of a patient interface, such as a mask or nasal prongs. A gas washout vent assembly of the system may include a variable exhaust area, such as one defined by gears, radial exhaust revolvers and/or flow diverters for a conduit having a variable gas passage channel. The vent assembly may be attached substantially near or included with the patient interface. An actuator of the assembly, such as a solenoid, motor or voice coil, manipulates the vent assembly. The actuator may be configured for control by a processor to change the exhaust area of the vent assembly based on various methodologies including, for example, sleep detection, disordered breathing event detection and/or leak detection.

CROSS REFERENCE TO RELATED APPLICATIONS

This present application is a divisional of U.S. patent application Ser.No. 13/967,609 filed Aug. 15, 2013 which claims the benefit of thefiling date of U.S. Provisional Patent Application No. 61/699,520 filedSep. 11, 2012, the disclosures of which are hereby incorporated hereinby reference.

FIELD OF THE TECHNOLOGY

The present technology relates to conduits for a respiratory treatmentapparatus such as a vent arrangement for a mask assembly that may beimplemented for a respiratory pressure treatment including, for example,Non-invasive Positive Pressure Ventilation (NPPV) and continuouspositive airway pressure (CPAP) therapy of sleep disordered breathing(SDB) conditions such as obstructive sleep apnea (OSA).

BACKGROUND OF THE TECHNOLOGY

Treatment of sleep disordered breathing (SDB), such as obstructive sleepapnea (OSA), by a respiratory treatment apparatus such as a continuouspositive airway pressure (CPAP) flow generator system involves adelivery of air (or other breathable gas) at pressures above atmosphericpressure to the airways of a human or other mammalian patient via aconduit and/or a mask. Typically, the mask fits over the mouth and/ornose of the patient, or may be an under-nose style mask such as a nasalpillows or nasal cushion style mask. Pressurized air flows to the maskand to the airways of the patient via the nose and/or mouth. As thepatient exhales, carbon dioxide gas may collect in the mask. A washoutvent in the mask or conduit may be implemented to discharge the exhaledgas from the mask to atmosphere.

The washout vent is normally located in the mask or substantially nearthe mask in a gas delivery conduit coupled to the mask. The washout ofgas through the vent to the atmosphere removes exhaled gases to preventcarbon dioxide build-up. “Rebreathing” of exhaled carbon dioxide may bea health risk to the mask wearer. Adequate gas washout may be achievedby selecting a vent size and configuration that allows a minimum safewashout flow at a low operating CPAP pressure, which typically can be aslow as 4 cm H₂O for adults and 2 cm H₂O for children.

WO 2006/102708 describes an air delivery system with a vent valve thatis controlled to maintain a substantially constant air flow in the airdelivery conduit and the air flow generator.

WO2005/051468 describes a vent assembly for use with a mask assembly.The vent assembly includes a first vent, a second vent and a selector toswitch the flow of exhaled gas from a patient between the first andsecond vents.

There is a need for a gas washout vent arrangement which allows foradequate venting of carbon dioxide while permitting efficient airdelivery to the patient. SUMMARY OF THE TECHNOLOGY

One aspect of the present technology relates to a washout ventarrangement for respiratory mask apparatus which incorporates a variableeffective venting area or aperture(s).

Further aspects of the present technology relate to an air deliveryapparatus incorporating a gas vent arrangement, and to apparatus,systems and methods for controlling variable venting of gases.

Some aspects of the present technology involve an apparatus forautomated control of gas washout of a patient interface of a respiratorytreatment apparatus. The apparatus may include a vent assembly having avariable exhaust area. The vent assembly may be associated with apatient interface to vent expiratory gas. The vent assembly may includea first gear having a first flow bore. The apparatus may also include anactuator to manipulate orientation of the flow bore of the first gear tovary the exhaust area.

In some cases, the apparatus may further include a second gear, thesecond gear may have a second flow bore. The first and second gears maybe adapted in a meshed configuration. In some cases, a rotation of thefirst and second gears closes of the first and second flow bores toprevent a transfer of gas through a conduit of the vent assembly. Insome cases, a rotation of the first and second gears opens the first andsecond flow bores to permit a transfer of gas through a conduit of thevent assembly. The first gear may include a set of teeth surrounding aperiphery of the first gear.

Optionally, such apparatus may further include a controller including aprocessor. The controller may be coupled with the actuator. Thecontroller may be configured to operate the actuator to change theexhaust area of the vent assembly. The actuator may include a motor. Ashaft of the motor may be coupled with the first gear to rotate thefirst gear. In some examples, the apparatus may also include a positionsensor. The position sensor may be configured to detect a rotationalposition of the first gear.

Some examples of the present technology involve an apparatus forautomated control of gas washout of a patient interface of a respiratorytreatment apparatus. The apparatus may include a vent assembly having avariable exhaust area. The vent assembly may be associated with apatient interface to vent expiratory gas. The vent assembly may includea radial exhaust revolver and a conduit casing. The apparatus may alsoinclude an actuator to manipulate orientation of the radial exhaustrevolver to vary the exhaust area.

In some cases, the apparatus may include a radial exhaust port. Theradial exhaust port may be adapted within the conduit casing of the ventassembly in which the radial exhaust revolver rotates. A peripheral edgeof the radial exhaust revolver may include raised and lower edges. Aproximity of a raised edge to the radial exhaust port may block at leastportion of radial exhaust port. A proximity of a lower edge to theradial exhaust port may open at least portion of radial exhaust port.

In some examples, the radial exhaust revolver may include a plurality ofapertures. The apertures may be adapted to permit gas flow through therevolver within the conduit casing. Optionally, the conduit casing mayinclude a restriction element. The restriction element may be arrangedwith the radial exhaust revolver to selectively permit or pre vent gasflow through at least one of the plurality of apertures depending on arotational orientation of the radial exhaust revolver with respect tothe restriction element. Each of the apertures of the plurality ofapertures may be formed by a triangular boundary of the radial exhaustrevolver. Edges of the triangular boundary of the apertures of theradial exhaust revolver may include a convex surface.

In some cases, an edge of the radial exhaust revolver may include anedge aperture. A rotational alignment of the edge aperture and theradial exhaust port may permit venting of gas from the conduit casing.In some cases, the apparatus may include a restriction elementinsertable within the conduit casing. The restriction element mayinclude a flow stop and a flow aperture. Optionally, a rotationalalignment position of the edge aperture and the radial exhaust port maypermit venting of gas from the conduit casing. This rotational alignmentposition may further correspond with an alignment of the flow stop withan aperture of the radial exhaust revolver to block flow through theradial exhaust revolver and the conduit casing.

Such apparatus may further include a controller having a processor. Thecontroller may be coupled with the actuator and be configured to operatethe actuator to change the exhaust area of the vent assembly. Theactuator may include a motor and a shaft of the motor may be coupledwith the radial exhaust revolver. The motor may be within the conduitcasing. The apparatus may also include a position sensor configured todetect a rotational position of the radial exhaust revolver.

Some examples of the present technology may involve an apparatus forautomated control of gas washout of a patient interface of a respiratorytreatment apparatus. The apparatus may include a vent assembly having avariable exhaust area. The vent assembly may be being associated with apatient interface to vent expiratory gas. The vent assembly may includea spherical diverter and a conduit casing. The spherical diverter mayhave a flow bore. The apparatus may also include an actuator tomanipulate orientation of the spherical diverter to vary the exhaustarea.

In some cases, rotation of the spherical diverter may position the flowbore to selectively permit a transfer of gas through the flow borewithin the conduit casing of the vent assembly. A rotation of thespherical diverter may selectively position a surface of the sphericaldiverter to selectively block a transfer of gas through one or moreexhaust ports of the conduit casing of the vent assembly. Optionally,the conduit casing may include a muffler chamber proximate to one ormore exhaust ports of the conduit casing. The apparatus may also includea controller with a processor. The controller may be coupled with theactuator and configured to operate the actuator to change the exhaustarea of the vent assembly. The actuator may include a motor and a shaftof the motor may be coupled with the spherical diverter. The apparatusmay also include a position sensor configured to detect a rotationalposition of the spherical diverter.

Other aspects, features, and advantages of this technology will beapparent from the following detailed description when taken inconjunction with the accompanying drawings, which are a part of thisdisclosure and which illustrate, by way of example, principles of thetechnology. Yet further aspects of the technology will be apparent fromthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further example embodiments of the technology will now be described withreference to the accompanying drawings, in which:

FIG. 1 is a schematic diagram of a respiratory treatment apparatus;

FIG. 2 shows incorporation of a variable area vent assembly into arespiratory mask and gas conduit arrangement;

FIG. 3 shows incorporation of a variable area vent assembly into anunder-nose nasal pillows style respiratory mask;

FIG. 4 is an illustration of meshed gear components for a variable areavent assembly;

FIGS. 5A and 5B are side view illustrations of the meshed gearcomponents of FIG. 4 in closed and open positions respectively;

FIG. 6 is an illustration of a conduit vent of the technology includingan radial exhaust revolver;

FIG. 7 is an illustration of the exhaust revolver of the conduit vent ofFIG. 6;

FIG. 8 is a cross sectional view of the conduit vent of FIG. 6;

FIG. 9 is an illustration of another example of a vent assemblyimplemented with a radial exhaust revolver;

FIGS. 10A and 10B are cross sectional illustrations of the conduit ventof FIG. 9 with the radial exhaust revolver in inspiratory (non-exhaustventing) and expiratory (exhaust venting) positions respectively;

FIGS. 11A and 11B are cross sectional illustrations of a conduit ventemploying a spherical diverter and showing the diverter in expiratory(exhaust venting) and inspiratory (non-exhaust venting) positionsrespectively;

FIGS. 12A and 12B are cross sectional illustrations of a conduit ventemploying a spherical diverter with J-channels and showing the diverterin inspiratory (non-exhaust venting) and expiratory (exhaust venting)positions respectively;

FIGS. 13A and 13B are graphs illustrating various functions forcontrolled vent flow verses patient respiratory flow in someembodiments; and

FIG. 14 is an illustration of a Cheyne-Stokes breathing pattern;

FIG. 15A is a graph illustrating a simulated Cheyne-Stokes breathingflow pattern;

FIG. 15B is a graph of a ventilation measure and a standard deviation SDof the ventilation measure taken from the simulated patient flow of FIG.15A; and

FIG. 16 is a schematic illustrating an example architecture of acontroller for controlling adjustment of the variable vents of thepresent technology.

DETAILED DESCRIPTION Example Respiratory Treatment Apparatus

FIG. 1 schematically illustrates an air delivery system of a respiratorytreatment apparatus for delivering breathable gas to a patient underpressure, for example, as used in CPAP therapy for sleep disorderedbreathing (SDB), in accordance with one example embodiment of thecurrent technology.

The basic components of the system of FIG. 1 are an air flow generator10, optionally a humidifier 15 which may be either integrated with orseparate from the flow generator, and an air delivery conduit 20 leadingfrom the flow generator—or from humidifier if fitted—to a patientinterface 30 which is in communication with the patient's airways.

The air flow generator may be of a type generally known in the art, suchas the RcsMed S9™ series flow generator, and may incorporate a housingwith an air inlet, a blower capable of delivering air to the patient ata pressure of, for example, 2 to 30 cm H2O, or 4 to 20 cm H2O, and anair outlet adapted for connection of air delivery conduit 20 orhumidifier 15.

The flow generator may further include sensors 45, such as pressure andflow sensors, and a microprocessor control (e.g., processor 40) whichmay be capable of receiving signals from sensors 45 and any remotesensors 50, and to use the information from those sensors in control ofthe flow generator 10 and/or humidifier 15.

The air delivery conduit 20 may be a flexible tube, for example 15 or 19mm or preferably between 8-22 mm internal diameter, for delivering thepressurized (and possibly humidified) air leaving to the patientinterface 30. The conduit 20 may also incorporate one or more heatingelements (not shown) for regulating temperature of the gas passingthrough the conduit and for preventing condensation (“rain-out”) insidethe tube.

The air delivery conduit 20 may also include one or more wires 55 forcarrying signals to and/or from the components (e.g., remote sensors 50)located at or adjacent the patient interface 30 back to/from theprocessor 40. Alternatively, the signals may be multiplexed andtransmitted over a heating wire of the air conduit. An example of aheated tube is disclosed in PCT application WO 2008/055308, filed 8 Nov.2007. Still further, signals from and/or to the sensors and controlcomponents of the vent arrangements may be communicated wirelessly.

The patient interface 30 may be, for example, a nasal, pillows, prongs,cradle, full face or oro-nasal mask sealingly engaging the patient'snares, nose, and/or mouth. Examples of some of these types of mask arethe ResMed Mirage Activa™, Mirage Swift™ II mask and Ultra Mirage™masks.

In the embodiment illustrated in FIG. 1, the patient interface alsoincludes a gas washout vent component—(schematically shown at 60),examples of which are described in more detail below. The air deliveryconduit 20 may have a control wire 65 for providing signals to controlthe gas washout vent and/or other active components at the patientinterface end of the conduit. Optionally, the control wire may alsocarry multiplexed signals representing measurements by sensorsassociated with the operation of the vent arrangements or sensors of thepatient interface. In the case of the implementation of control of themovement of one or more components of the vent assembly, a controllermay be configured with control instructions to implement one or more ofthe venting control methodologies described in International PatentApplication No. PCT/US2012/055148, filed on 13 Sep. 2012 and/orAustralian Provisional Patent Application No. AU 2013900885, filed on 14Mar. 2013, the disclosures of which are incorporated herein byreference.

Alternatively, the gas washout vent assembly 60 may be positioned in theair delivery path proximal to the patient interface 30. For example, itmay be positioned between the patient interface end of conduit 20 andthe patient interface 30.

Alternatively, the gas washout vent assembly 60 may be displaced orpositioned remote from the patient interface 30. For example, the ventassembly 60 may be positioned at the flow generator 10.

Variable Area Gas Washout Vent

In some examples of the present technology, the gas washout ventcomponent may be a variable venting area gas washout vent and/or avariable venting rate gas washout vent. Such variable gas washoutventing may have one or more of the following advantages. A fixed ventwill typically require an increase in flow (and power) of the flowgenerator in order to increase CO₂ washout and a decrease in flow of theflow generator to decrease washout. However, a variable vent mayincrease or decrease CO₂ washout without such power increases ordecreases simply by opening or closing the vent. Changes to CO₂ washoutmay also be made more rapidly and/or with more precision with a variablevent when compared to waiting for the flow generator to change pressureand flow to do so with a fixed vent. Moreover, when combining flowgenerator changes with the adjustment of a variable vent, even quickerand/or more precise adjustments to washout may be achieved. Furthermore,use of a variable mask vent can permit a patient to feel lessclaustrophobic since a more open vent with a greater vent flow can makea mask feel more open.

Moreover, such a vent may allow for a reduction of the flow of air tothe patient. It may reduce turbulence of air and thereby decrease noise.It may also reduce turbulence in the mask to better simulate normalbreathing. Alternatively, control of the vent can increase turbulence inthe mask to improve venting such as for better CO₂ washout. It mayrequire less power from the flow generator. It may allow for smallerflow generators and their associated components (e.g., humidifiers). Itmay reduce the cost of the therapy system (e.g., due to the smallercomponents). It may also be used to reduce the exhalation pressure whichincreases comfort and may thereby increase or improve CO₂ washout.

Apparatus Incorporating Variable Area Gas Washout Vent

FIG. 2 is a schematic illustration of one example of incorporation of avariable area gas washout vent assembly into a respiratory treatmentapparatus in accordance with one aspect of the current technology.

In the arrangement of FIG. 2, the respiratory treatment apparatusincludes a flow generator 10 and humidifier 15 system generally asdescribed above for FIG. 1. An air delivery conduit 220 deliverspressurized air from the flow generator to a patient interface forapplying the generated air pressure to the patient's airways. In theillustrated embodiment the patient interface is of the triangular fullface or nasal type respiratory mask 230. However, other types of patientinterface may be applicable.

The mask 230 includes an elbow connecting element 222 for connection ofthe mask to the air supply.

The gas washout vent assembly 260, generally in accordance with theembodiments described above, can be provided with one or more endconnectors (not shown) for connection to the air delivery conduit 220and the elbow connecting element 222 for location in the airway pathbetween the air delivery conduit and the elbow so that it may besubstantially near the patient interface. Alternative positions may beimplemented (e.g., between the elbow and the mask.) An example actuator299, such as a motor, solenoid or pneumatic piston, is also illustratedsymbolically in the embodiment of FIG. 2. The gas washout vent assembly260 thus allows venting of exhaled gases from the patient.

The vent assembly 260 and delivery conduit 220 may further includemating electrical connectors for power take off and conveyance offeedback and control signals, as further described below.

FIG. 3 illustrates a further example gas washout vent according to someexamples of the current technology implemented with a respiratorytreatment apparatus. In this embodiment, an under-nose patientinterface, such as a nasal cushion, nasal pillows or prongs, includesthe gas washout vent.

Similar to the previously described embodiments, the example of FIG. 3includes an air delivery conduit 320 leading from a flow generator (notshown) to the patient interface 330, which in the illustrated exampleincludes nozzles 335 for sealing against the patient's nares.

In contrast to the example of FIG. 2, in FIG. 3 the vent assembly 360 isincorporated in the patient interface 330, attached to the distal end ofthe patient interface 330, opposite from the pivotable elbow 322. Thevent assembly 360 may take the form of any of the venting componentsdescribed in more detail herein and vent the gases from the end of theassembly rather than the circumference. In some cases, an outlet mufflermay be added to assist in reducing noise at the vent. For example, atube or conduit may be added at the output of the vent to take noisefurther away from the mask or ears of the patient. This may also permitexpired air to be channeled away from patient's face.

Example Vent Assembly Features

(a) Geared Assembly Examples

FIGS. 4, 5A and 5B show a variable vent assembly 60 in accordance withone example of the present technology. Such examples may employ one ormore gears 410-1, 410-2. The gears may be integrated into a conduitpassage CP that may lead to or be part of a vent as describedpreviously. The gears may typically include gear teeth 412 around thecircumference of the gear. However, fewer teeth may be implementeddepending on the desired degree of rotation of each gear. One or more ofthe gears may also include a flow bore, the positioning of which mayadjust the characteristics of the vent. As shown in the example of FIG.4 each gear includes a flow bore 414-1, 414-2. Generally, each flow bore414-1, 414-2 may serve as a flow passage FP through its respective gear410-1, 410-2. The flow bore may be implemented generally perpendicularto an axis (A-R) of rotation of the gear. In this regard, one or more ofthe gears may include a keyed channel 416-1, 416-2 about which the gearmay rotate when fitted to a rotation shaft (not shown) such as a driveshaft of a motor (e.g., a stepper motor). Such a drive shaft may have ashape to correspond to the shape of the keyed channel so that the gearmay rotate with the drive shaft. Optionally, the channel of the gearsmay be round, rather than keyed, such that the gear may simply rotate ona fixed shaft or axle.

As illustrated in more detail in the side views of FIGS. 5A and 5B, theflow bore(s) may optionally be tapered to form a tapered portion 418-1,418-2 that deviates from the generally straight portion 420-1, 420-2 ofthe flow bore. Tapering can permit different adjustments to the flowcharacteristics of the flow passage FP depending on the rotationalpositioning of the gear with respect to a conduit passage CP of the ventin which the gear is implemented.

In this regard, rotation of one or more of the gears may serve to adjustan area or size of the flow passage FP defined by the flow bore(s). Forexample, the rotational repositioning of the gears may be by a motorthat may be external to the conduit passage CP. In the case of theimplementation of two gears, the gears may be aligned in a meshedposition such that the rotation of one gear rotates the other gear. Inthis case, only one motor can be implemented. The motor may becontrolled by a controller, such as the controller of the respiratorytreatment apparatus.

The rotational adjustment of the gear(s) may thereby increase ordecrease area and/or rate of flow through the gear(s) emanating from aconduit passage CP to the vent opening VO past the gears. For example,as illustrated in FIG. 5A, the gears may be rotated so as to close theflow passage FP as the flow path of the flow bore is rotated to begenerally perpendicular to the flow path of the conduit passage CP. Insuch a case the gear structure blocks the flow from the conduit passageCP. Further rotation of one or more of the gears may then permit flowthrough the flow passage FP as the flow path of the flow bores open whenthey become aligned with the flow path of the conduit passage. In theexample, a rotation of ninety degrees may serve to change the flowpassage FP from fully open to fully closed or from fully closed to fullyopen. Rotational adjustments within the range between zero and ninetydegrees may permit varying degrees of flow through the flow passage FPsince the flow path will be partially closed or partially open to somedegree. However, depending on the configuration of the flow bore(s),other ranges of rotational motion may be implemented.

The gears and any conduit in which they are implemented may be formed ofany suitable material and may advantageously be formed of a mouldedplastic material such as polycarbonate, nylon or porous formed plasticssuch as polypropylene or similar.

(b) Radial Exhaust Revolver Venting Examples

FIGS. 6, 7 and 8 provide several views of a vent assembly 60 employing aradial exhaust revolver 662. The radial exhaust revolver 662 may beinserted within a conduit casing 664, such as a cylindrical casing, thatwill include a flow passage FP. Air or breathable gas may be selectivelyvented at a radial venting portion VP at a periphery of the conduitcasing 664. Such a radial venting portion may be formed by one or moreside aperture(s) shown as radial exhaust port 665 on an external surfaceportion of the conduit casing 664 adjacent to the radial exhaustrevolver 662. Typically, the conduit casing may include a flowrestriction element 667 within conduit casing 664. This may be insertedor formed integrally with the conduit casing 664. The flow restrictionelement 667 may also be formed with one or more adjacent restrictionelement aperture(s) 669.

The radial exhaust revolver 662 may be inserted adjacent the flowrestriction element within the conduit casing 664. In this regard, asbest seen in FIG. 7, the radial exhaust revolver 662 may be formed in acircular or disk shape having one or more revolver apertures 666 and oneor more revolver flow stops 670. Optionally, such apertures and stopsmay be triangular or other shape and they may alternate around thesurface of the disk as illustrated in the example of FIG. 7. Therevolver may be formed of a soft material such as a urethane material.Such a material may help to reduce operational noise of the revolver. Inthis regard, the inside surfaces edges of the boundary of the revolverapertures 666 may have a curved surface or other convex shape so as toavoid edges which might increase noise as gas passes through therevolver openings.

When installed, the radial exhaust revolver may be rotated, such as onan axis AX1 corresponding to shaft opening 661, in direction of arrowsRA within its assembled position in the conduit casing 664. Thisrotation may selectively block or allow flow through the radial exhaustrevolver 662 from the flow path FP of the conduit casing 664. Theselective permitting of flow may be achieved when one or morerestriction element apertures 669 align with one or more revolverapertures 666. The selective blocking of flow may be achieved when therevolver flow stops 670 fully align with the restriction elementaperture(s) 669. A partial alignment may permit less gas flow throughthe revolver than when the apertures (e.g., restriction elementapertures 669 and revolver apertures 666) are fully aligned.

The disk of the revolver may further include a series of raised edges REand lowered edges LE along its periphery. Such edges may selectivelyalign with one or more radial exhaust ports 665 so as to selectivelyblock or permit radial exhaust through the ports. For example, when araised edge RE revolves to be fully aligned with the exhaust port 665,no flow through the exhaust port 665 is permitted. Similarly, when alowered edge LE revolves to be at least partially aligned with theexhaust port 665, gas of the conduit casing may vent out of the exhaustport 665. Such venting is radial or perpendicular to the axis ofrotation of the revolver. The extent of the overlap of the raised edgeRE with the exhaust port thereby increasing or decreasing the passablearea of the exhaust port can permit varying degrees of exhaust throughthe port. The extent of this overlap may be controlled by controllersetting the rotational position of the revolver.

Such a revolver when inserted in or between a patient interface ordelivery conduit may then serve as a variable area vent. For examplewhen the shaft of a motor (not shown), such as a stepper motor, is inthe conduit casing and coupled to the revolver, the revolver may beselectively controlled by a controller of a respiratory apparatus torotate the revolver to any desired position. In such a case, the firstend 886 of the conduit casing may be coupled with an output of a flowgenerator or delivery conduit and the second end 888 may be coupled witha mask, such as a full face or nasal mask. The revolver may be rotated,such as during detected patient inspiration, to a position to permitflow through the conduit casing and through the revolver so that apressurized flow from the flow generator may reach the patient at themask. In such a position, the exhaust port 665 of the casing may besubstantially or fully blocked by the revolver edge. The revolver may befurther rotated, such as during detected patient expiration, to aposition to reduce or prevent flow through the conduit casing andrevolver so that a pressurized flow from the flow generator is reducedat the patient mask. In such a position, the exhaust port 665 of thecasing may be substantially or partially open to varying degrees by themovement of the revolver edge to permit radial exhaust venting of gasthrough the conduit casing from the patient mask.

Another example radial exhaust revolver 962 may be considered inreference to FIGS. 9, 10 and 11. The radial exhaust revolver 962 may beinstalled for rotation in direction of rotation arrows RA in a conduitcasing 964 for variable venting. The conduit casing 964 further includesan insertable flow restriction element 967. However, such an element maybe integrated with the form of the conduit casing 964. Radial venting ispermitted when one or more radial apertures 992 of the revolver 962align with the exhaust port 965 of the conduit casing 964. Gas flowthrough the conduit is permitted when the revolver 962 rotates, such asa shaft (not shown) of shaft opening 961, to align revolver aperture 966with restriction element aperture 969.

For example, as shown in FIG. 10A, the conduit casing 964 may be coupledto a respiratory apparatus so as to have a flow generator end FGE and amask end MSKE. When the revolver edge aperture 992 at the edge of therevolver rotates to be aligned with a wall portion of the conduit casing964 as seen in FIG. 10A, no radial exhaust venting is permitted. In thisposition, a pressurized flow of breathable gas from the flow generatorend FGE of the conduit casing passes through the revolver aperture 966that is aligned with the restriction element aperture 969 toward themask end MSKE.

When the revolver edge aperture 992 at the edge of the revolver rotatesto be aligned with the exhaust port 965 of the conduit casing 964 asseen in FIG. 10B, radial exhaust venting is permitted. In this position,no flow through the revolver aperture 966 or restriction elementaperture 969 is permitted since the flow stop 970 of the revolver blocksthe restriction element aperture 969 and a restriction wall 1010 surfaceof the flow restriction element 967 blocks the revolver aperture 966. Inthis position, an expiratory exhaust flow of gas from the mask end FGEof the conduit casing passes through the revolver edge aperture 992 andthe aligned exhaust port 965 to vent from the conduit casing. Such aposition may permit air from patient expiration to be vented from theconduit casing via the exhaust port 965 such as when the motor coupledto the revolver rotates the revolver to the position via control of acontroller that detects expiration.

Depending on the size of the exhaust port or exhaust ports that areadjacent to the revolver aperture, the venting area may be varied. Forexample, multiple ports, such as with different port sizes, may beimplemented in the conduit casing to permit variable area venting orother proportional flow venting. In such a case, the revolver aperturemay be positioned adjacent to a larger exhaust port area for moreventing flow or a smaller exhaust port area for less venting. In somecases, the revolver may be equipped with a position sensor to providepositioning feedback for feedback control of the revolver. For example,the revolver may be equipped with a reflective surface for a phototransistor/diode to generated a position feedback signal for acontroller. Other position sensors may also be implemented. For example,one or more Hall Effect sensors may be implemented for sensing theposition of the revolver.

(c) Spherical Diverter Examples

FIGS. 11A and 11B illustrate a variable area vent assembly 60 inaccordance with another example. In this example a spherical diverter isemployed. The flow diverter may be rotatable about an axis AX2 toselectively permit, prevent or otherwise variably adjust venting areawith respect to the exhaust ports 1165 on a conduit casing 1164 (shownas a cross sectional half of the assembly). Although not shown, the axisAX2 may represent a pin or other shaft through shaft opening 1161.Rotation of the pin or shaft may thereby rotate the spherical diverterin a direction as illustrated with respect to directional arrows RA. Thespherical diverter 1110 includes a flow bore 1114 through the sphericaldiverter. Depending on the position of the surface portions of thespherical diverter 1110, different pathways through or from the conduitcasing may be blocked or partially blocked by the surface portions.

Thus, the flow bore 1114 may serve to channel gas flow through theconduit casing from a flow generator end FGE of the conduit casing 1164to the patient interface or mask end MSKE of the conduit casing 1164 asillustrated in FIG. 11B. In this case, the surface of the sphericaldiverter 1110 may block or partially block a gas flow path from theinside of the conduit casing through one or more of the exhaust ports1165. Similarly, the rotational position of the spherical diverter maypermit the flow bore 1114 to serve as a channel to direct gas flow fromthe mask end MSKE through one or more of the exhaust ports 1165 asillustrated in FIG. 11A. In this case, the surface of the sphericaldiverter 1110 may block a flow path through the conduit between the flowgenerator end FGE and the mask end MSKE.

For example, a motor or rotary solenoid coupled to a shaft of the shaftopening 1161 may be controlled by a controller to position the sphericaldiverter to the exhaust port open position of FIG. 11A during, forexample, detected patient expiration to permit expiratory air to ventfrom the conduit casing. Similarly, the motor or rotary solenoid coupledto the shaft of the shaft opening 1161 may be controlled by thecontroller to position the spherical diverter to the exhaust port closedposition of FIG. 11B during, for example, detected patient inspiration.Positions of the spherical diverter between those shown in FIGS. 11A and11B can permit partial opening area of the exhaust ports to permitvarying of the degree of exhaust venting.

In some cases, as illustrated in the example of FIGS. 11A and 11B, theconduit casing may include one or more exhaust chambers 1198 proximateto the exhaust ports 1165. The exhaust chamber may serve as a box suchas for a foam material FM or other noise suppression material to reducenoise associated with gas venting from the exhaust ports 1165. In somesuch cases, the wall of the exhaust chamber, when exterior to theconduit casing as shown in FIGS. 11A and 11B, can include a vent opening1199 to permit the exhaust to escape to atmosphere after traversingthrough the foam material FM of the exhaust chamber 1198.

The example spherical diverter embodiment of FIGS. 12A and 12B issimilar in construction and operation to that of the example of FIGS.11A and 11B respectively. However, in the example of the FIGS. 12A and12B, the spherical diverter includes one or more J-channel or J-boreportions 1277-1, 1277-2 as opposed to the generally convex portion CCPof the spherical diverter of FIGS. 11A and 11B. The J-channel portionsmay be concave recesses in the spherical diverter. Such J-channelportions may create turbulence to permit the gas flow of the conduit toassist with the rotation of the spherical diverter.

Actuation of Vent Flow Adjustment

In its simplest form, the relative open, closed and partial openpositions of the vent components described herein may be manipulatedmanually and thus allow adjustment control, of the vent flowcharacteristics. In some embodiments, the vent may have a manual settingfor the vent area which may provide a DC component (offset) to the ventflow. Fine or course adjustments to the vent flow of such a vent maythen be controlled by a controller by increasing or decreasing the ventarea from the manually set vent area. The adjustment of the vent areamay be continuously variable depending on the relative displacement ofthe moveable components (e.g., diverters, revolvers and gears) of thevent assembly. For example, a retaining mechanism may be employed topermit the adjustment of these components on their respective shafts tobe made by selection of a particular position from a plurality ofdiscrete set positions. Optionally, visual markings may be employed toindicate variable vent settings based on the relative rotationalpositions.

The range of adjustments may be preset by the clinician, to set thevariable vent characteristics in accordance with a prescription for thepatient's therapy.

In some embodiments of the current technology, the vent assembly mayinclude an actuator for adjustment of the vent characteristics.

For example, the vent assembly may be biased towards the open position,such as by means of a torsion spring, to form a normally open vent whichoperates also as an anti-asphyxia valve for the patient mask. Such openpositions may be considered with reference to, for example, FIGS. 6,10B, 11A, 12A. The actuator may then act against the force of thebiasing means, to close the vent either fully or proportionally.

Suitable actuators may be implemented by different types of components.For example, a voice coil may serve as the actuator including linear androtary or swing arm voice coil actuators. Alternatively, piezo actuators(both direct and/or amplified) may be implemented. Further alternativesinclude pneumatic actuation (including pneumatic amplification). In suchembodiments, a bleed conduit from the flow generator pressure may beprovided to the mask to power a piston actuator. The piston may rotateor slide the vent assembly into the desired position as controlled bythe pressure applied to the bleed conduit by one or more servo-valves,proportional valves or flow control valves.

In some embodiments where a solenoid may be utilised as the actuator, avoltage may be transmitted by a controller of the flow generator to thesolenoid positioned to manipulate the vent assembly such as by adjustingthe rotational position of the components of the vent assembly. Thevoltage transmitted to the solenoid may alter the position of thesolenoid and hence the position of the vent assembly. For example, afirst voltage may be applied to the vent assembly to position the ventassembly at a first position (e.g., half of the vent assembly open toatmosphere). A second voltage may be applied to the vent assembly toposition the vent assembly at a second position (e.g., all of the ventassembly open to atmosphere). Such adjustable positions of the vent maybe discrete but they may also be continuously variable and may runbetween fully opened and fully closed or some other set limits therebetween.

In the case of an electrically powered actuator type such as voice coilor piezo actuator, the actuator may be provided with its own powersource such as battery. Optionally, it may be powered by an electricalpower take-off, for example, from the heating circuit of the airdelivery conduit 20. The vent assembly and air delivery conduit may beformed with mating electrical connectors for this purpose. Stillfurther, the actuator may be powered by inductive or transformercoupling.

In one example implementation of an actuator, a voice coil actuator maybe configured to achieve the relative displacement of the vent assembly,such as the rotation of the structures of the gas washout vent assembly60. For example, one or more coil wires may be attached at the outsideof the conduit of FIG. 6 or 9. A magnet may be positioned in a fixedlocation, for example, on a portion of the radial exhaust revolver. Whena voltage is applied to the wire, the magnetic forces may then cause therepositioning of the revolver and thereby change the alignmentsassociated with the vent openings. Different positions of the revolvermay be set by controlling an application of different voltages orcurrents to the coil or coils.

In another actuator example, an induction coil may be attached to thevent apparatus. Optionally, a motor, such as a piezo motor, may also beattached to the induction coil. Some embodiments may be implemented withjust a coil and/or just a piezo motor/driver. In some cases, embodimentsmay be implemented without a position sensor such as by controlling asolenoid and measuring the vent flow rather than vent position. In sucha case, a flow sensor may be implemented at or near the exhaust ports orventing ports of the assembly. Alternatively, embodiments may beimplemented with just a motor or driver that adjusts the position of thevent.

The control signals for the adjustment of the vent may then be learnedby running a ‘learn’ or ‘initiation’ cycle. Such a cycle may optionallybe implemented by the controller of the flow generator. Such a systemmay learn the amount of power required to adjust the vent and mayoptionally do so without the need (or expense) for a position sensor.Such a learn cycle may be initiated at the commencement of therapy. Insuch a cycle, a series of voltages may be sent to the motor (e.g.,modulate the voltage) to induce a series of voltages in the inductioncoil to cause the vent assembly to move or step through the alignmentpositions of the vent from completely closed to completely open. Thedata concerning the minimum and maximum voltages may then be recorded orsaved in association with the minimum and maximum vent positions.Similarly, the minimum voltage required to initially move the vent maybe recorded. Data representing voltage that is required or desired tomove the vent from the minimum to maximum positions (or vice versa) mayalso be recorded. In the event that the current is controlled, thecurrent required for setting the movement of the vent to any desiredposition associated with a particular voltage may alternatively berecorded. In setting the vent assembly for use, the controller of theflow generator may calculate the required vent flow based on thecharacteristics of a certain mask such as by the methods described in WO2002/053217. Based on learned values and the known characteristics ofthe vent, the controller may control applying of a voltage or current tothe motor or solenoid to position the vent to obtain the desired flow.

A piezo motor may be advantageous for such an embodiment as it requireslower power to run such as in the case that power is only needed to movethe vent and power is not needed to oppose a biasing force to maintainthe vent in a certain position. A piezo motor however may be lessaccurate than a biasing force and rotational solenoid actuator, as aspring and solenoid arrangement may be able to operate with moreaccuracy in a small stroke.

Feedback for Control of Vent Flow.

The vent assembly 60 may further include one or more sensors, such as apressure sensor or flow sensor to measure the flow or pressure for usein the control of the vent. For example, pressure of the mask may bemeasured and used as a function to control the vent. Similarly, flow inor through the vent may be measured and used to control the vent.Moreover, a measure of patient flow may be applied as an input to afunction for making control changes to the vent. Optionally, a positionsensor may be implemented to sense the relative position of the moveablecomponent of the vent assembly. Based on one or more of such sensors,the venting characteristics of the vent may be evaluated duringoperation, such as by the controller or processor of the flow generator.

Communication between the processor 40 of the flow generator and thevent assembly actuator and sensors may be through dedicated wires, oralternatively may be multiplexed with other sensor wires or multiplexedwith the tube heater wires or inductively coupled to the heater wires.Alternatively, communication may be by wireless communications, such aswith a Bluetooth link.

In one example embodiment, the actuator assembly may also include aninfrared light that pulses infrared light rays in the direction of thevent assembly. The reflectivity may be measured such as by the amplitudeof the received light, which may then be implemented as an indicator ofthe vent position where different amplitudes are associated withdifferent positions of the vent. Once the position of the vent assemblyis known, a processor of the flow generator may be configured tocalculate the pressure and/or flow at the mask and adjust the settingsof the flow generator accordingly. In addition, the actuator or motormay adjust the position of the vent assembly if the flow generatorcalculates that an alternative vent position is required.

Control of Vent Flow

The variable area vent arrangement of the current technology may improvethe control of gas washout. This, in turn, may permit improved patienttreatment and/or functioning of a respiratory treatment apparatus. Forexample, the vent may be operated to achieve a more instantaneousresponse with a flow generator to conditions at the mask. It may beoperated with the flow generator to achieve faster rise and fall times.In some cases, operation of the vent can permit use of a blower thatoperates with a single pressure while still allowing the pressure at themask to be varied by controlling changes to the venting area. In somecases, the changes in a vent conduit impedance may also allow for anadjustment to the pressure levels in the mask. For example, the conduitembodiments of FIGS. 11B and 12B may be coupled to a mask but not theflow generator. Thus, the conduit end labeled as the flow generator endFGE may itself escape to atmosphere as an output vent rather than beingcoupled to the flow generator. As such, changes in the conduit impedancethat may be made by manipulation of the diverter to permit either achange in impedance from the smaller exhaust ports to the largerdiameter of the end FGE of the conduit can thereby change the pressureat or flow of the vent.

In some embodiments, control of the vent area may be implemented insynchronization with a patient's breathing cycle so as to participate inthe pressure treatment of the patient. For example, the actuation of theactive vent may be implemented so that the vent flow mirrors the flow ofthe patient's respiratory flow cycle as illustrated in FIGS. 13A and13B. As illustrated in FIGS. 13A and 13B, the vent flow is out of phasewith patient respiration. Thus, a minimal vent flow may be set for peakinspiration so that the patient may inhale more of the gases from theflow generator (as opposed to a typical non-adjustable gas washout ventwhere some of the gas from the flow generator passes straight out of thevent), and a maximum vent flow may be set for peak expiration. Asillustrated in the graphs, different functions (e.g., sinusoidalfunction, shark-fin function, etc.) may be implemented for setting thechange in amplitude of the vent flow. Also shown in the graph is acontinuous vent flow (CVF) that could be implemented with a fixed ventor by setting the active vent to a fixed position.

Optionally, the control of the venting area and the resulting vent flowcould also be phased or timed depending on the sleep state of thepatient (e.g., whether they are awake, sleeping, etc.). For example,when the patient is awake (e.g., trying to get to sleep) the vent may becontrolled to operate in a more open or higher flow position incooperation with the flow generator, such as a higher flow position heldapproximately constant over the patient's breathing cycle, so that thereis less impedance when the patient inhales. As the patient enters asleep state, the controller of the system may then initiate operation ofthe vent so that it functions in the manner illustrated in FIG. 13A or13B. Optionally, if the device then detects an awake state or non-sleepstate, the vent may be controlled to return to operate in the higherflow position in cooperation with the flow generator, such as the moreconstant higher flow position. A determination of sleep state may bemade by any suitable process but may in some embodiments be made inaccordance with the sleep condition detection technologies described inPCT Patent Application No. PCT/AU2010/000894, filed on Jul. 14, 2010,the disclosure of which is incorporated herein by reference.

In some embodiments, the control of the vent could be implemented inresponse to detected patient conditions, such as sleep disorderedbreathing events. For example, an analysis of flow and/or pressure databy a processor of the controller of the flow generator may detectrespiratory conditions such as central or obstructive apnea, central orobstructive hypopnea, and/or snoring etc. Example methods for detectingsuch conditions are described in U.S. patent application Ser. No.12/781,070, filed on May 17, 2010, the entire disclosure of which isincorporated herein by reference. The controller may then set the ventarea based on the analysis of the patient's detected condition. Forexample, if a central apnea is detected (an open airway apnea) or acentral hypopnea, the processor may control the vent to close or reducethe vent area so that the patient is permitted to re-breath CO₂. Thismay induce the patient's brain to detect an increase in CO₂ in the bodyand thereby cause the patient to spontaneously breath. Thereafter, ifthe controller detects a patient's breath or if a safety time periodlapses without a breath, the vent may then be controlled to return toits normal operation, such as that associated with the varied operationof FIG. 13A or 13B or a more constant open position that provides arequired vent flow during respiration. Beneficially, pressure or flowadjustments that are attributable to changes of the vent area may takeeffect faster than such changes controlled by adjustments to some flowgenerators. Thus, an initial adjustment of mask conditions bymanipulation of the vent may be performed before flow generator changesare implemented. This may provide the controller of the flow generatoran opportunity to determine with its sensors how a patient's airway isreacting and/or how the flow generator should thereafter respond.

In one embodiment, adjustments to the venting area may be implemented toimprove patient comfort or to offset a potential leak due to animproperly positioned mask. Essentially, these procedures may permitadjustments to the position of the patient's mask. For example, thecontroller of the flow generator may detect an occurrence of anunintentional leak that may be attributable to a displaced positioningof the mask. If such a leak is detected, the controller may control anadjustment to the vent area such as to close or rapidly close the ventassembly. Optionally, such a closing of the vent may be joined by asimultaneous controlled increase in speed of a flow generator totemporarily increase airflow or pressure delivered to the mask. Thepressure increase at the mask resulting from the closing of the ventassembly may then cause the mask to ‘jump’, shake or disrupt from thepatient's face. This jump or movement of the mask may result in the maskre-positioning its seal to the patient's face and potentially sealingthe detected leak path.

As an alternative controlled approach, the controller may then controlthe vent arrangement to open (and/or simultaneously control a reductionin generated pressure by the flow generator) so that the pressure of themask is substantially reduced (e.g., to a pressure or atmosphericpressure) for some predetermined period of time. This substantialreduction of pressure in the mask may then allow the mask to bere-positioned by some movement of the patient or allow the mask tochange in the case of an auto adjusting mask and thereby potentiallycorrect the seal issue. Optionally, this controlled opening approach maybe implemented subsequently to a prior ‘jump’ attempt previouslydescribed, in the event that mask leak is still detected after the‘jump’ attempt. Such controlled procedures may be repeated or performed(in any order) until the leak is no longer detected or for apredetermined number of times. Moreover, in some embodiments, bothopening and closing the vent may be repeated rapidly and may coincidewith the flow generator decreasing and increasing the pressurerespectively. Such a shaking process may result in the mask vibrating toa degree to help in reset the mask position to rectify the detectedleak.

Other vent area control procedures may also be implemented in responseto leak detection, such as the detection of unintentional leak,performed by the controller. For example, in some embodiments, thedegree of venting may be variably controlled as a function of adetection of unintentional leak and/or mouth leak (such as in the caseof a nasal only mask). In such an embodiment, the pressure and flowoutput from the flow generator may be determined. Additionally, the ventleak may be calculated by sensing pressure or flow at or near the ventassembly. The difference between the air flow generated by the flowgenerator and the vent leak flow may be determined to be the sum ofunintentional leak and mouth leak (where applicable). Mouth leak may bedetermined, for example, as described in U.S. Provisional Patent.Application No. 61/369,247, filed 30 Jul. 2010, the entire disclosure ofwhich is incorporated herein by reference. Thus, the unintentional leakflow may be calculated. (e.g., Flow_(unintentional) _(_)_(leak)=Flow_(total) _(_) _(generated)−(Flow_(mouth) _(_)_(leak)+Flow_(vent) _(_) _(leak)))

The vent area of the vent assembly may then be controlled based on sucha determination of unintentional leak quantity by the processor of theflow generator. In one example, upon the flow generator processordetermining increased or excessive unintentional leak, such as by acomparison of the quantified leak to a threshold that may be indicativeof a required gas washout flow, the processor may control the ventactuator to reduce the vent open area, since less gas washout venting isrequired with increased unintentional leak at the patient's face.Similarly, if such a leak is no longer detected, the processor maythereafter control an increase to the vent open area so that the flow ofthe gas washout vent satisfies a required gas washout flow.

In a further example, by knowing the open area against pressurecharacteristic for the vent assembly, the processor may control the ventactuator based on the sensed or calculated pressure at the vent, tocontrol the vent flow to remain constant or to follow a predeterminedpattern.

In a yet further example, the venting may be controlled in response tothe patient's breathing cycle or therapy need.

Algorithms for determining cycling between inhalation and exhalation areknown, and described for example in US Patent Application 2008/0283060,filed 21 Dec. 2006. By employing such an algorithm, the variable areavent controller may be controlled to synchronise with the breathingcycle, for example to reduce the vent open area or close the ventcompletely during part of the patient's breathing cycle. In one example,the vent area is reduced or closed at a time corresponding to inhalationwhen gas washout is not required, and is opened coinciding with patientexhalation.

By reducing gas venting during inhalation, it is believed that the meanand peak flow rate required to be generated by the flow generator may bereduced, with resultant decreases in flow generator capability and size,air delivery conduit diameter and humidifier capacity being possible.Furthermore, the power and water consumption of the apparatus may beable to be reduced.

The actuation of the active vent may be controlled by software. In someembodiments, the software may be upgradable or re-settable in accordancewith particular patient's needs. For example, a patient with COPD mayhave a first vent flow requirement in their first year of treatment andthen have a second vent flow requirement in their second year oftreatment. The software may control this change of the vent flow settingaccording to year by checking an internal clock and adjusting thesetting accordingly. Alternatively, the data of the software may beupgraded to re-program the active vent in the second year of treatmentto cause the vent to achieve the second vent flow requirement. Asdiscussed in more detail herein, controlled adjustments to the vent mayalso be made during a treatment session and may depend on detectedpatient conditions such as sleep stage or time in treatment. Moreover,vent adjustments may also optionally be made based on pulse oximetermeasurements of the patient during treatment. For example, a controllermay reduce vent size to cause re-breathing of CO₂ upon detection ofhigher than normal paO₂ measurements and/or lower than normal paCO₂relative to one or more thresholds. The controller may then return thevent size for normal CO₂ washout when the pulse oximeter measurementsnormalize.

In some cases, an anti-asphyxia valve may no longer be necessary. Theactive vent could also serve as an anti-asphyxia valve. For example,such an embodiment may be implemented such as when the vent includes abiasing member. The biasing member may maintain the vent in a normallyopen position for breathing through the vent if the controller is notpowered and/or operating the flow generator. When under power andoperating, the controller may then control the vent to limit vent flowto any desired CO₂ washout level.

Patient Comfort Vent Control

Patient compliance with OSA therapy such as CPAP and APAP is affected bymany factors. One of the significant factors affecting success of an OSApatient remaining on effective therapy is the level of comfortassociated with the wearing of the device and mask during the periodwhile still awake. If the patient comfort can be paramount until theonset of sleep then there is likely to be an increased compliance withCPAP or APAP therapy overall. Similarly, the patient may resistcontinuation of therapy if woken for any reason during sleep. Theawakening may be unrelated to the patient condition, for example thearrival home of another family member may wake the patient. Once awake,the patient may suffer discomfort and remove the CPAP system.

One factor that may decrease patient comfort, especially when notsleeping or in an aroused state, is the potentially low pressure duringwake state of an APAP machine. Typically an APAP machine uses lowpressure when the wearer is not experiencing an occluded airway. Forfixed aperture vented mask systems the low pressure also will result ina low intentional leak (or vent) flow and may result in decreased CO₂washout. Potentially, the patient may experience some re-breathing,while not significantly of clinical concern it may be sufficientlyuncomfortable to the patient and discourage use of the mask system.

Potentially, due to the low washout levels and additionally the level ofhumidity and heating levels of the air proximal to the patient airwaysin the conduit and mask, the patient may feel uncomfortable.

During treatment and the period waiting to fall asleep and also duringpotential arousal events, the patient may suffer a feeling similar toclaustrophobia where there is a desire to remove the CPAP/APAP system.

A variable vent system, such as one that employs the conduits and ventspreviously described, can potentially improve comfort during sleep stateperiods, including wake, when therapy is not required. For example, acontroller of the adjustable vent may detect appropriate sleep relatedperiods of a patient, such as wake, or potentially light sleep. Inresponse to these detections, the controller may then alter thepneumatic, humidity and heat settings set by the controller.

For example, the controller may increase the vent flow when therespiratory treatment apparatus is set to generate lower pressures.Similarly, the controller may decrease the vent flow when therespiratory treatment apparatus is set to generate higher pressures.This may be suitable if these pressure settings contribute to eventsthat may wake or result in patient arousal.

When increasing the vent flow at lower pressures, the APAP/CPAPrespiratory treatment device could compensate by increasing the flowsupply from the controlled flow generator to maintain the set pressureat the patient interface but with increased flow through the conduit andmask and out the vent. The result is significantly increased CO₂ washoutat the desired pressure setting.

This controlled adjustment may also result in a change in feeling of thepatient as the flows near the facial skin and nasal nares may have acooling and drying effect. Similarly, reducing the vent flow mayincrease the feeling of the temperature and moisture content of the airto the patient.

By changing the vent flow, the patient may feel hotter/cooler, moist ordry changing simply with the flow rate of the air near sensitive skinand nasal tissue. Thus, the regulation of vent flow can provide a basisfor adjusting patient comfort.

In some embodiments, the detection of sleep state may serve as a basisto change the vent flow to improve the patient's feeling of comfort.Similarly, the humidity and delivered air temperature may also beoptimised to suit the patient during such conditions in the event thatthe controller of the respiratory treatment apparatus also controls ahumidifier and/or air warming element.

If normal or deeper sleep states are detected by the controller, theprescribed patient therapy (e.g., CPAP and APAP therapy settings),humidity and temperature settings will be set and delivered by theapparatus.

However, comfort changes from the prescribed treatment settings may beset when the apparatus detects light sleep or awake states. Thephysician prescribed settings during these states may not be necessarysince OSA is not likely to occur during such stages of sleep (or awake)states. Thus, patient preferred settings may automatically take effecton the detection of the light sleep or awake states.

Such features as a “ramp” and similar from current CPAP machines do notdeliver the prescribed titration level of pressure until the patient isexpected to be in the correct sleep state by delaying the delivery oftherapeutic pressure levels for a period of time by gradually raisingthe pressure to the therapeutic level.

A further feature can exploit the lack of need for therapeutic pressuresduring light sleep or awake states to allow the patient to adjust theflow through the vent during such states. Normal therapeutic settingscan resume during usual sleep states requiring it. For example, when the“ramp” feature is engaged, the respiratory treatment apparatus may setthe vent flow levels to those specified by some “patient comfort”settings rather than the prescribed therapeutic settings. Thus, theapparatus may have a user interface to allow the patient to input oradjust the “patient comfort” settings (e.g., within permitted ranges) tothe apparatus for these controlled features.

As an extension and as part of the “patient comfort” settings, theapparatus may permit the patient to adjust CPAP/APAP pressure within thesafe limits that may be set by clinical staff during titration or tosome range that may be found to be safe during the detected awake orlight sleep periods.

Similarly, as part of the “patient comfort” settings, the patient may beable to have favored humidity and heat settings during such sleep phasesthat revert to needs based settings in other sleep states.

In some cases, the settings may be automatically controlled or adjustedby the respiratory treatment apparatus based on detected environmentalconditions such at temperature and/or humidity outside of the device.For example, cooler settings may be utilized during warmer seasons andwarmer settings may be utilized during cooler seasons.

There may be a plethora of settings and/or “patient comfort” profiles ofsettings that may be preferred by the patient, or even the clinical orprescribing staff. The different profiles even for a single patient maybe activated by the device depending on various detected conditions,such as a particular sleep state, environmental conditions, etc.

For example, the apparatus may be configured to activate a particularpreferred profile of the air delivery parameters that improve patientcomfort at a preferred automatic time or particular sleep state.

Priority in control or profile may be given to comfort, pressure, flow(CO₂ washout), moisture, heat, battery or power supply endurance, noise,machine/consumable part life or other system parameter that may bepreferred.

In a particular example, an OSA respiratory treatment apparatus may beconfigured to deliver pressure, vent flow (CO₂ washout),humidity/moisture and/or heat to the tastes of the patient as set in“patient comfort” settings by a user interface of the apparatus. Anycombination of parameters pressure, flow, moisture and temperature ofdelivered air may be profiled individually or in any combination. Thepatient comfort settings then may be activated depending on theparticular detected conditions of the machine such as sleep state (e.g.,awake or light sleep) and/or environmental conditions. When prescribedtherapy is required, such as during detected sleep states, physicianprescribed “therapeutic settings” may then be activated such that someor all of the comfort settings will be deactivated.

Therapeutic Vent Control

Cheyne-Stokes respiration (CSR), Complex Sleep Apnoea and other forms ofcentral sleep apnoea may be characterised as (on-average)hyperventilation during sleep. This hyperventilation frequentlymanifests itself as a lower-than-normal daytime PaCO₂. However, it ismainly CHF- or altitude-related periodic breathing with thatassociation—that can be predicted from daytime PaCO₂. Complex SleepApnoea cannot typically be predicted from daytime PaCO₂. The graph ofFIG. 14 shows the typical waxing and waning pattern of CSR in a patientgetting CPAP treatment from a CPAP respiratory treatment apparatus. Thepattern is characterized by periods of hyperventilation (hyperpnoea)interspersed with periods of low ventilation (hypopnoea) or centralapnoea. The pattern is strikingly periodic with little variation neitherin the length of each cycle nor in the length of the components of eachcycle.

Therapeutic methods to return PaCO₂ to a normal range have focussed onrestoring a normal breathing pattern. For example, the ResMed AutoSet CS(or VPAP Adapt) is a non-invasive pressure-control ventilator thatstabilises PaCO₂ by increasing pressure support during periods of apnoeaor hypopnoea and decreasing pressure support during periods ofabove-normal or normal ventilation. This method acts to ‘break’ thevicious cycle whereby hyperventilation drives the patient's PaCO₂ belowthe apnoeic threshold which in-turn leads to a new cycle ofhyperventilation. By servo-ventilating short term ventilation to atarget which is a fraction of a longer term ventilation, the CSR patternis often abolished. The ventilator has sensors and methods to reliablymeasure patient respiratory flow in the presence of a known mask ventflow and a variable inadvertent mask leak. The ventilation measures arederived from the patient respiratory flow estimate.

Another way to abolish or ameliorate the CSR pattern is by having thepatient re-breathe some fraction of their own exhaled CO₂. Therebreathed CO₂ acts to either raise the patient's PaCO₂ or to preventPaCO₂ from falling during hyperventilatory phases. In this way it canreduce the drive to hyperventilate. A convenient way to do this is tohave an actively controlled vent at the mask such as one of theembodiments previously described. In existing vented breathing systems,the vent is a fixed orifice which provides enough flow over the expectedmask pressure range to adequately purge the mask of exhaled CO₂ overeach breathing cycle. By controlling the vent orifice, the amount of CO₂rebreathed by the patient can also be controlled. Such an activelycontrolled vent can form part of a servo-control system of a respiratorytreatment apparatus.

In one example, the respiratory treatment apparatus, such as aventilator, may implement a fixed hyperventilation threshold setting,such as in litres per minute (LPM). This setting may be set by aclinician before the start of therapy. If the patient's average measuredventilation (measured over a period such as three minutes) were toexceed the threshold, the vent may be actively controlled by thecontroller to reduce the flow such as by reducing its venting size suchthat the patient would start to re-breath a small fraction of their ownCO₂. If the detected hyperventilation subsequently resolved, such as ifthe threshold is no longer exceeded, the vent could be controlled by thecontroller to return to a normal position.

In another alternative approach, a servo-control mechanism of thecontroller may continuously adjust the vent size to keep fresh gasventilation under a pre-determined threshold. Such a servo-controlledsystem might utilise a PID type controller with the error signal beingthe degree to which ventilation was above threshold and it would outputthe size of the vent. The controller could also regulate the vent sizeso as to constrain it to be within pre-determined maximum and minimumsizes.

In another example, instead of a fixed ventilation threshold, theremight be an index of ventilation instability. For example, the followingindices may serve as a single measure or combined measure of ventilationinstability:

a. Ventilation stability may be measured by a moving windowstandard-deviation of ventilation assessed by the controller;

b. A central apnoea index, a central hypopnoea index or a centralapnoea-hypopnoca index as detected by the controller;

c. An apnoea-hypopnoea index (which persists despite automaticadjustment of EPAP to abolish upper airway obstruction) as detected bythe controller;

d. A respiratory disturbance index, (e.g., an arousal index such as onederived from flow, SpO₂ and/or photoplethysmogram) as detected by thecontroller.

Methods for detection and automated determination of such indices may beconsidered in view of the discussion of PCT/AU2010/000894, filed Jul.14, 2010, based on U.S. Provisional Patent Application No. 61/226,069filed Jul. 16, 2009, the disclosures of which are incorporated herein byreference.

In each case, the vent orifice size may be adjusted either in stepfashion or continuously so as to minimise the measure of ventilationinstability. Optionally, the controlled changes to vent size could bebetween two size chosen for ‘normal’ breathing and “re-breathing” or itmay be continuously adjustable through many sizes in a range betweenfixed preset limits.

FIGS. 15A and 15B show a simulated CSR flow pattern and some filteroutputs plotted on a common time scale. The trace in FIG. 15A is asimulated patient flow with CSR breathing bracketed by two periods ofnormal breathing. The plot of FIG. 15B shows a ventilation measure VM(filtered with a three minute time constant) and the moving windowstandard deviation SD of the ventilation measure taken from thesimulated patient flow of FIG. 15A. Allowing for the time it takes thefilters to initialize (slow rise at the beginning), it can be seen thatthe ventilation during the CSR period is a) higher on-average and b)variable. The standard deviation SD trace shows that the instability inthe ventilation can be measured by a moving window SD metric.

As previously mentioned, in some embodiments, the adjustable vent may becontrolled by an actuator and servo-controlled to minimise a respiratorydisturbance index. For example, in the plot of FIG. 15B, the determinedrise in the widowed standard deviation SD of ventilation would cause thecontroller to reduce the vent size to increase the fraction of inspiredCO₂. Then, when the windowed SD reduced, the controller would beginreopening or increasing the area of the vent.

In another example, the controller of the respiratory treatmentapparatus may ‘phase lock’ to the CSR cycle. This process would involvelearning the CSR cycle via a phase-locked loop and then adjusting thevent area so as to initiate a rebreathing cycle for the optimum time andwith the optimum phase relationship to the CSR cycle. This would resultin a lower on-average amount of rebreathing compared to a fixed level ora quasi-statically adjusted level.

In such a case, the CSR cycle is typically 60 seconds in length with atypical range of between 40 and 90 seconds. In general, the cycle lengthincreases with worsening heart failure HF (e.g., bad O reference) asdoes the hyperpnoea length. The cycle length does not vary quickly orsubstantially within a night. Therefore, once a system had phased lockedto a CSR cycle, it may be possible to maintain phase lock despite alessening degree of CSR amplitude modulation. Alternatively, if the CSRsignal were to disappear altogether (i.e., normal breathing resumed)then the apparatus may re-establish a phase lock quickly based on apreviously learned cycle length, hyperpnoea length and apnoea orhypopnoea length, or metrics indicative of these features.

If the patient is experiencing a CSR pattern with frank apnoeas, it mayonly be possible to initiate rebreathing during the hyperpnoea phase(i.e., while the patient is actually spontaneously breathing). However,once apnoeas have been abolished by the apparatus and a CSR pattern withcontinuous spontaneous breathing throughout the breathing cycle isdetected, then it may be advantageous to vary the controlled rebreathingprocess to the optimum point in the cycle and for the optimal lengththat minimises the instability to the greatest extent. This phase delayand length of the rebreathing cycle might be pre-programmed or learnedafter starting at a predetermined ‘best guess’ starting point.

In some cases, the apparatus may simply monitor the patient over time byrecording the CSR metrics previously mentioned. The apparatus may thenevaluate the metrics and recommend use of a vent having a lesser ventingflow if residual CSR exists. For example, the apparatus may reference anarray of standard vents to choose from with particular vent flowcharacteristics, the apparatus may determine that a step down to asmaller vent should be implemented by issuing a warning or textinstruction. Optionally, in the case of constant flow venting, it maysuggest an adjustment to the vent such as a manual adjustment orinsertion of an alternate mylar tab or vent aperture that will make somechange to the flow characteristics of the vent.

In the above examples, the active vent control system can be run at eachtreatment session (e.g., each night) to provide therapy to the patientin a real time detection/response to patient needs. However, in someembodiments, it might be used on one or more nights to determine asuitable fixed vent size for the patient's subsequent therapy (e.g., byimplementing a vent flow titration protocol.)

In the examples above, the active vent system and associated controlsystem for rebreathing could be used in conjunction with adaptiveservo-ventilation (e.g., ResMed AutoSet CS2). In such a combined system,the pressure control adjustment process might be used as the primarydriver for suppression of CSR breathing and a rebreathing controlprocess as previously described might supplement that process, intandem, to damp out any residual instability (if it is detected).Alternatively, the two systems might work in concert with a masterprocess controlling both pressure-support and rebreathing via activevent in order to more simultaneously operate to stabilise ventilation tothe greatest degree. For example, such a system might implement apressure support control-loop acting with a ‘fast’ time constant and arebreathing control process acting with a ‘slow’ time constant.

In another example, the rebreathing control process might be the primarymeans of suppressing CSR breathing, with the ventilator pressure supportcomponent acting to suppress frank apnoeas via the insertion of backupbreaths.

In some embodiments, phasic venting may be implemented with a ventingprotocol to treat CSR. For example, during detected hyperpnoea periods,the controller may adjust the vent to close or reduce the venting areato treat the hyperpnoea but only during detected patient expiration. Insuch a case, the vent area would be increased during inspiration.

In another embodiment, a process of the controller may directly regulaterebreathing by calculating or estimating the quantity of flow outthrough the vent and controlling it to be at a desired quantity orpercent.

In embodiments with the aforementioned technology, a pressure treatmenttherapy is generated by a respiratory treatment apparatus that alsoincludes the venting control. However, in some embodiments a mask with avented control may be used without a flow generator that generates apressure treatment (e.g., a snorkel) or in some cases pressure treatmentmay be stopped while venting control is activated.

Example Controller Architecture

An example system architecture of a controller of a respiratorytreatment apparatus suitable for controlling actuation of the variablearea vent assembly of the present technology is illustrated in the blockdiagram of FIG. 16. In the illustration, the controller 1606 for arespiratory treatment apparatus may include one or more processors 1608.The system may also include a display interface 1610 to output eventdetection reports (e.g., central apnea, obstructive apnea, centralhypopnea, obstructive hypopnea, etc.) or vent assembly related data(settings, vent flow vs. time plots, vent area, etc.) as describedherein such as on a monitor or LCD panel. This may be used to log and/ormonitor the performance or controlled changes in the ventcharacteristics during a treatment session. A user control/inputinterface 1612, for example, a keyboard, touch panel, control buttons,mouse etc. may also be provided to activate or modify the controlmethodologies described herein. The system may also include an actuator,sensor or data interface 1614, such as a bus, for receiving/transmittingdata such as programming instructions, pressure and flow signals,positioning signals, actuator control signals, etc. The device may alsotypically include memory/data storage components 1620 containing controlinstructions of the aforementioned methodologies. These may includeprocessor control instructions for sensor signal processing (e.g., flowand/or pressure signal processing and filtering, vent assembly positiondetermination, vent assembly flow determination, vent assembly pressuredetermination, etc.) at 1622. These may also include processor controlinstructions for control of the variable vent area vent assemblyactuation/setting (e.g., patient condition detection, leak detection,patient respiratory cycle detection, learn cycle, sleep detection, maskadjustment procedures, related threshold comparisons, etc.) at 1624 aspreviously discussed in more detail herein. These may also includeprocessor control instructions for treatment control (e.g., respiratorytreatment control, pressure adjustments, CPAP pressure control, Bi-levelpressure control, or other flow generator control methodologies etc.) at1626. Finally, they may also include stored data 1628 for or from themethodologies of the controller (e.g., vent assembly settings, ventassembly voltage and/or current data, vent assembly positions, gaswashout flow requirements data, recorded vent flow data, etc.).

In some embodiments, these processor control instructions and data forcontrolling the above described methodologies may be contained in acomputer readable recording medium as software for use by a generalpurpose computer so that the general purpose computer may serve as aspecific purpose computer according to any of the methodologiesdiscussed herein upon loading the software into the general purposecomputer. Still further, the methodologies may be contained in a deviceor apparatus that includes integrated chips, a memory and/or othercontrol instruction, data or information storage medium. For example,programmed instructions encompassing such detection methodologies may becoded on integrated chips in the memory of the device or apparatus toform an application specific integrated chip (ASIC). Such instructionsmay also or alternatively be loaded as software or firmware using anappropriate data storage medium.

In this specification, the word “comprising” is to be understood in its“open” sense, that is, in the sense of “including”, and thus not limitedto its “closed” sense, that is the sense of “consisting only of”. Acorresponding meaning is to be attributed to the corresponding words“comprise”, “comprised” and “comprises” where they appear.

While particular embodiments of this technology have been described, itwill be evident to those skilled in the art that the present technologymay be embodied in other specific forms without departing from theessential characteristics thereof. The present embodiments and examplesare therefore to be considered in all respects as illustrative and notrestrictive, the scope of the technology being indicated by the appendedclaims rather than the foregoing description, and all changes which comewithin the meaning and range of equivalency of the claims are thereforeintended to be embraced therein. It will further be understood that anyreference herein to subject matter known in the field does not, unlessthe contrary indication appears, constitute an admission that suchsubject matter is commonly known by those skilled in the art to whichthe present technology relates.

1. An apparatus for automated control of gas washout of a patientinterface of a respiratory treatment apparatus comprising: a ventassembly having a variable exhaust area, the vent assembly beingassociated with a patient interface to vent expiratory gas, the ventassembly including a first gear having a first flow bore; and anactuator to manipulate orientation of the flow bore of the first gear tovary the exhaust area.
 2. The apparatus of claim 1 further comprising asecond gear, the second gear including a second flow bore, the first andsecond gears adapted in a meshed configuration.
 3. The apparatus ofclaim 2 wherein a rotation of the first and second gears closes of thefirst and second flow bores to prevent a transfer of gas through aconduit of the vent assembly.
 4. The apparatus of claim 3 wherein arotation of the first and second gears opens the first and second flowbores to permit a transfer of gas through a conduit of the ventassembly.
 5. The apparatus of claim 1 wherein the first gear comprises aset of teeth surrounding a periphery of the first gear.
 6. The apparatusof claim 1 further comprising a controller including a processor, thecontroller coupled with the actuator, the controller configured tooperate the actuator to change the exhaust area of the vent assembly. 7.The apparatus of claim 6 wherein the actuator comprises a motor, a shaftof the motor coupled with the first gear to rotate the first gear. 8.The apparatus of claim 7 further comprising a position sensor, theposition sensor configured to detect a rotational position of the firstgear.
 9. An apparatus for automated control of gas washout of a patientinterface of a respiratory treatment apparatus comprising: a ventassembly having a variable exhaust area, the vent assembly beingassociated with a patient interface to vent expiratory gas, the ventassembly including a radial exhaust revolver and a conduit casing; andan actuator to manipulate orientation of the radial exhaust revolver tovary the exhaust area.
 10. The apparatus of claim 1 further comprising aradial exhaust port, the radial exhaust port adapted within the conduitcasing of the vent assembly in which the radial exhaust revolverrotates.
 11. The apparatus of claim 10 wherein a peripheral edge of theradial exhaust revolver comprises raised and lower edges.
 12. Theapparatus of claim 11 wherein a proximity of a raised edge to the radialexhaust port blocks at least portion of radial exhaust port.
 13. Theapparatus of claim 12 wherein a proximity of a lower edge to the radialexhaust port opens at least portion of radial exhaust port.
 14. Theapparatus of claim 9 wherein the radial exhaust revolver comprises aplurality of apertures, the apertures adapted to permit gas flow throughthe revolver within the conduit casing.
 15. The apparatus of claim 14wherein the conduit casing comprises a restriction element, therestriction element arranged with the radial exhaust revolver toselectively permit or prevent gas flow through at least one of theplurality of apertures depending on a rotational orientation of theradial exhaust revolver with respect to the restriction element.
 16. Theapparatus of claim 15 wherein each of the apertures of the plurality ofapertures are formed by a triangular boundary of the radial exhaustrevolver.
 17. The apparatus of claim 16 wherein edges of the triangularboundary of the apertures of the radial exhaust revolver comprise aconvex surface.
 18. The apparatus of claim 9 wherein an edge of theradial exhaust revolver comprises an edge aperture.
 19. The apparatus ofclaim 18 wherein a rotational alignment of the edge aperture and theradial exhaust port permits venting of gas from the conduit casing. 20.The apparatus of claim 19 further comprising a restriction elementinsertable within the conduit casing, the restriction element comprisinga flow stop and a flow aperture.
 21. The apparatus of claim 20 wherein arotational alignment position of the edge aperture and the radialexhaust port permits venting of gas from the conduit casing, saidrotational alignment position further corresponding with an alignment ofthe flow stop with an aperture of the radial exhaust revolver to blockflow through the radial exhaust revolver and the conduit casing.
 22. Theapparatus of claim 9 further comprising a controller including aprocessor, the controller coupled with the actuator, the controllerconfigured to operate the actuator to change the exhaust area of thevent assembly.
 23. The apparatus of claim 22 wherein the actuatorcomprises a motor, a shaft of the motor coupled with the radial exhaustrevolver.
 24. The apparatus of claim 23 wherein the motor is within theconduit casing.
 25. The apparatus of claim 23 further comprising aposition sensor, the position sensor configured to detect a rotationalposition of the radial exhaust revolver.